Abstract 557: Essential Role For Caveolar Microdomains And Microtubules In Cardiac Protection
The subcellular localization and organization of signaling molecules involved in cardiac protection are poorly understood. Caveolae, ~100 nm invaginations of the sarcolemmal membrane, are known to localize cardiac protective signaling molecules and interact with cytoskeletal components. We used the volatile anesthetic isoflurane, an agent that produces protection from cardiac ischemia/reperfusion (I/R) injury as a means to test the hypothesis that sarcolemmal caveolar microdomains are essential for protection from simulated I/R injury in cardiac myocytes (CM). CM isolated from adult rat hearts using collagenase perfusion and maintained in culture for 24 hr were exposed to vehicle control, methyl-β-cyclodextrin (MβCD) to bind cholesterol and disrupt caveolae, or colchicine to depolymerize microtubules and disrupt caveolae formation. CM were then exposed to 30 min of isoflurane (1.4%) in a metabolic chamber, followed by simulated I/R injury (SI/R: 1 hr of hypoxia with glucose deprivation followed by 1 hr of reoxygenation in normal media). Cell death was assessed by trypan blue staining. Electron microscopy was used to assess formation of caveolae. Isoflurane reduced CM death in response to SI/R but treatment with MβCD, which disrupted caveolae (Fig 1⇓), eliminated the protective effects of isoflurane (Iso, Fig. 2⇓). Colchicine also disrupted caveolae and eliminated isoflurane-induced protection (Fig 1–2⇓). Isoflurane-induced cardiac protection from SI/R injury in CM is eliminated by disruption of sarcolemmal caveolae, implying that intact caveolae, their distribution, and their interaction with microtubules are critical for cardiac protection from I/R injury.